computer audio question

There's been much progress in DAC and DAC chips design since The Bel Canto DAC 2 came out almost 10 years ago.

That said, Your most cost-effective upgrade at this point could be to add something like the M2Tech Hiface USB/SPDIF converter and output your computer's bitstream data through a USB port. This isolates your computer RFI/EMI from the DAC, helps control jitter, and has other benefits which all should help your source sound more musical.

As others noted above, it all begins with a good lossless audio file being output from one of many good software packages such as Foobar or JRiver for PC, or ITunes for the Mac.

"Newer NOT always better"
Okay, but in the Bel Canto series cited by the OP, newer e.one series DACs are definitely better in just about every meaningful respect, except perhaps cost.

"Better to go with known great sounding chips, such as PCM1704, PCM179X"
Interesting that Bel Canto's e.one DAC3 represents an upgrade to the PCM1792.